Sometimes there is a need to combine multiple WiX installers into one. However one problem arises: the new – “combined” installer should upgrade ( remove ) old installers. In order to achieve that you have to use upgrade section in your WiX script.
First of all you have to create upgrade section for current installation then upgrade section for each product you have to upgrade. In the following example take a look on UpgradeCode in the first upgrade section and Id attribute in Product. The second upgrade section upgrades (removes) other product.
<Product Id=“e4824422-4901-4b15-954a-18a46aa74e8d“ Name=“WixProject2“ Language=“1033“ Version=“1.0.0.0“ Manufacturer=“PUT-COMPANY-NAME-HERE“ UpgradeCode=“448fe241-3ef5-4f0b-8160-96f5d42ecb04“>
<Package InstallerVersion=“200“ Compressed=“yes“ />
<Upgrade Id=“448fe241-3ef5-4f0b-8160-96f5d42ecb04“>
<UpgradeVersion Minimum=“1.0.0“ OnlyDetect=“yes“ Property=“NEWERVERSIONDETECTED“/>
<UpgradeVersion Minimum=“1.0.0“ IncludeMinimum=“yes“ Maximum=“1.0.0“ IncludeMaximum=“yes“ Property=“OLDERVERSIONBEINGUPGRADED“/>
</Upgrade>
<Upgrade Id=“a882e462-67d8-4aed-89c2-fa75a912eed0“>
<UpgradeVersion Minimum=“1.0.0“ OnlyDetect=“yes“ Property=“NEWERVERSIONDETECTED1“/>
<UpgradeVersion Minimum=“1.0.0“ IncludeMinimum=“yes“ Maximum=“1.0.0“ IncludeMaximum=“yes“ Property=“OLDERVERSIONBEINGUPGRADED1“/>
</Upgrade>
More info on upgrade can be found here